1. Technical Field
The present invention relates to a projector that projects an image formed by a light modulation unit on a screen.
2. Related Art
There is a projector of related art that has an optical filter for attenuating green light detachably disposed downstream of a projection lens and optically switches the display mode between a bright mode and a color-priority mode while maintaining the contrast of a projected image (see JP-A-2004-94175).
There is another projector of related art including a mechanism that inserts and retracts an optical filter for improving color reproducibility to and from the optical path upstream of a transmissive liquid crystal panel for a particular color (see JP-A-2001-13585). JP-A-2001-13585 describes white balance adjustment in a high-brightness mode in which a high priority is given to the brightness.
There is another known projector that addresses a problem of possible unevenness in brightness and color due to the angle of incidence of linearly polarized light projected on a screen when the projection light from the projector is formed of red, blue, and green light whose polarization directions differ from one another. To reduce the unevenness, a quarter-wave plate is disposed on the light-exiting side of a dichroic prism that combines the red, blue, and green light to convert the combined light into circularly polarized light (see JP-A-2007-304607).
The projector described in JP-A-2004-94175, however, has a structure in which the optical filter is placed in front of the projection lens. The structure is sometimes problematic in storing the optical filter and protecting the projection lens when the optical filter is not in use.
In the projector described in JP-A-2001-13585, since the optical filter is disposed upstream of the liquid crystal panel, it is necessary to provide a space around the liquid crystal panel for accommodating the mechanism for inserting and retracting the optical filter. As a result, the optical system needs to be arranged under constraints, or the projector tends to increase in size.
In the projector described in JP-A-2007-304607, since the quarter-wave plate as an optical filter is inserted between liquid crystal panels and a projection lens, where the optical density is relatively high, the quarter-wave plate needs to be made of an expensive material so that its reliability is maintained, and the back-focal length of the projection lens needs to be increased. As a result, the constraint on the layout of the optical system may increase and the cost may increase accordingly.